/*************************************************************************
 *                                                                       *
 * Open Dynamics Engine, Copyright (C) 2001-2003 Russell L. Smith.       *
 * All rights reserved.  Email: russ@q12.org   Web: www.q12.org          *
 *                                                                       *
 * This library is free software; you can redistribute it and/or         *
 * modify it under the terms of EITHER:                                  *
 *   (1) The GNU Lesser General Public License as published by the Free  *
 *       Software Foundation; either version 2.1 of the License, or (at  *
 *       your option) any later version. The text of the GNU Lesser      *
 *       General Public License is included with this library in the     *
 *       file LICENSE.TXT.                                               *
 *   (2) The BSD-style license that is included with this library in     *
 *       the file LICENSE-BSD.TXT.                                       *
 *                                                                       *
 * This library is distributed in the hope that it will be useful,       *
 * but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the files    *
 * LICENSE.TXT and LICENSE-BSD.TXT for more details.                     *
 *                                                                       *
 *************************************************************************/


/*******************************************************************
 *                                                                 *
 * cylinder-sphere collider by Christoph Beyer (boernerb@web.de)   *
 *                                                                 *
 * In Cylinder/Sphere-collisions, there are three possibilies:     *
 * 1. collision with the cylinder's nappe                          *
 * 2. collision with one of the cylinder's disc                    *
 * 3. collision with one of the disc's border                      *
 *                                                                 *
 * This collider computes two distances (s, t) and based on them,  *
 * it decides, which collision we have.                            *
 * This collider always generates 1 (or 0, if we have no collison) *
 * contacts.                                                       *
 * It is able to "separate" cylinder and sphere in all             *
 * configurations, but it never pays attention to velocity.        *
 * So, in extrem situations, "tunneling-effect" is possible.       *
 *                                                                 *
 *******************************************************************/

#include <ode/collision.h>
#include <ode/rotation.h>
#include <ode/objects.h>
#include "config.h"
#include "matrix.h"
#include "odemath.h"
#include "collision_kernel.h"	// for dxGeom
#include "collision_util.h"

int dCollideCylinderSphere(dxGeom* Cylinder, dxGeom* Sphere, 
                           int flags, dContactGeom *contact, int skip)
{
    dIASSERT (skip >= (int)sizeof(dContactGeom));
    dIASSERT (Cylinder->type == dCylinderClass);
    dIASSERT (Sphere->type == dSphereClass);
    dIASSERT ((flags & NUMC_MASK) >= 1);

    //unsigned char* pContactData = (unsigned char*)contact;
    int GeomCount = 0; // count of used contacts

#ifdef dSINGLE
    const dReal toleranz = REAL(0.0001);
#endif
#ifdef dDOUBLE
    const dReal toleranz = REAL(0.0000001);
#endif

    // get the data from the geoms
    dReal radius, length;
    dGeomCylinderGetParams(Cylinder, &radius, &length);
    dVector3 &cylpos = Cylinder->final_posr->pos;
    //const dReal* pfRot1 = dGeomGetRotation(Cylinder);

    dReal radius2;
    radius2 = dGeomSphereGetRadius(Sphere);
    const dReal* SpherePos = dGeomGetPosition(Sphere);

    // G1Pos1 is the middle of the first disc
    // G1Pos2 is the middle of the second disc
    // vDir1 is the unit direction of the cylinderaxis
    dVector3 G1Pos1, G1Pos2, vDir1;
    vDir1[0] = Cylinder->final_posr->R[2];
    vDir1[1] = Cylinder->final_posr->R[6];
    vDir1[2] = Cylinder->final_posr->R[10];

    dReal s;
    s = length * REAL(0.5); // just a precomputed factor
    G1Pos2[0] = vDir1[0] * s + cylpos[0];
    G1Pos2[1] = vDir1[1] * s + cylpos[1];
    G1Pos2[2] = vDir1[2] * s + cylpos[2];

    G1Pos1[0] = vDir1[0] * -s + cylpos[0];
    G1Pos1[1] = vDir1[1] * -s + cylpos[1];
    G1Pos1[2] = vDir1[2] * -s + cylpos[2];

    dVector3 C;
    dReal t;
    // Step 1: compute the two distances 's' and 't'
    // 's' is the distance from the first disc (in vDir1-/Zylinderaxis-direction), the disc with G1Pos1 in the middle
    s = (SpherePos[0] - G1Pos1[0]) * vDir1[0] - (G1Pos1[1] - SpherePos[1]) * vDir1[1] - (G1Pos1[2] - SpherePos[2]) * vDir1[2];
    if(s < (-radius2) || s > (length + radius2) )
    {
        // Sphere is too far away from the discs
        // no collision
        return 0;
    }

    // C is the direction from Sphere-middle to the cylinder-axis (vDir1); C is orthogonal to the cylinder-axis
    C[0] = s * vDir1[0] + G1Pos1[0] - SpherePos[0];
    C[1] = s * vDir1[1] + G1Pos1[1] - SpherePos[1];
    C[2] = s * vDir1[2] + G1Pos1[2] - SpherePos[2];
    // t is the distance from the Sphere-middle to the cylinder-axis!
    t = dVector3Length(C);
    if(t > (radius + radius2) )
    {
        // Sphere is too far away from the cylinder axis!
        // no collision
        return 0;
    }

    // decide which kind of collision we have:
    if(t > radius && (s < 0 || s > length) )
    {
        // 3. collision
        if(s <= 0)
        {
            contact->depth = radius2 - dSqrt( (s) * (s) + (t - radius) * (t - radius) );
            if(contact->depth < 0)
            {
                // no collision!
                return 0;
            }
            contact->pos[0] = C[0] / t * -radius + G1Pos1[0];
            contact->pos[1] = C[1] / t * -radius + G1Pos1[1];
            contact->pos[2] = C[2] / t * -radius + G1Pos1[2];
            contact->normal[0] = (contact->pos[0] - SpherePos[0]) / (radius2 - contact->depth);
            contact->normal[1] = (contact->pos[1] - SpherePos[1]) / (radius2 - contact->depth);
            contact->normal[2] = (contact->pos[2] - SpherePos[2]) / (radius2 - contact->depth);
            contact->g1 = Cylinder;
            contact->g2 = Sphere;
            contact->side1 = -1;
            contact->side2 = -1;
            GeomCount++;
            return GeomCount;
        }
        else
        {
            // now s is bigger than length here!
            contact->depth = radius2 - dSqrt( (s - length) * (s - length) + (t - radius) * (t - radius) );
            if(contact->depth < 0)
            {
                // no collision!
                return 0;
            }
            contact->pos[0] = C[0] / t * -radius + G1Pos2[0];
            contact->pos[1] = C[1] / t * -radius + G1Pos2[1];
            contact->pos[2] = C[2] / t * -radius + G1Pos2[2];
            contact->normal[0] = (contact->pos[0] - SpherePos[0]) / (radius2 - contact->depth);
            contact->normal[1] = (contact->pos[1] - SpherePos[1]) / (radius2 - contact->depth);
            contact->normal[2] = (contact->pos[2] - SpherePos[2]) / (radius2 - contact->depth);
            contact->g1 = Cylinder;
            contact->g2 = Sphere;
            contact->side1 = -1;
            contact->side2 = -1;
            GeomCount++;
            return GeomCount;
        }
    }
    else if( (radius - t) <= s && (radius - t) <= (length - s) )
    {
        // 1. collision
        if(t > (radius2 + toleranz))
        {
            // cylinder-axis is outside the sphere
            contact->depth = (radius2 + radius) - t;
            if(contact->depth < 0)
            {
                // should never happen, but just for safeness
                return 0;
            }
            else
            {
                C[0] /= t;
                C[1] /= t;
                C[2] /= t;
                contact->pos[0] = C[0] * radius2 + SpherePos[0];
                contact->pos[1] = C[1] * radius2 + SpherePos[1];
                contact->pos[2] = C[2] * radius2 + SpherePos[2];
                contact->normal[0] = C[0];
                contact->normal[1] = C[1];
                contact->normal[2] = C[2];
                contact->g1 = Cylinder;
                contact->g2 = Sphere;
                contact->side1 = -1;
                contact->side2 = -1;
                GeomCount++;
                return GeomCount;
            }
        }
        else
        {
            // cylinder-axis is outside of the sphere
            contact->depth = (radius2 + radius) - t;
            if(contact->depth < 0)
            {
                // should never happen, but just for safeness
                return 0;
            }
            else
            {
                contact->pos[0] = C[0] + SpherePos[0];
                contact->pos[1] = C[1] + SpherePos[1];
                contact->pos[2] = C[2] + SpherePos[2];
                contact->normal[0] = C[0] / t;
                contact->normal[1] = C[1] / t;
                contact->normal[2] = C[2] / t;
                contact->g1 = Cylinder;
                contact->g2 = Sphere;
                contact->side1 = -1;
                contact->side2 = -1;
                GeomCount++;
                return GeomCount;
            }
        }
    }
    else
    {
        // 2. collision
        if(s <= (length * REAL(0.5)) )
        {
            // collision with the first disc
            contact->depth = s + radius2;
            if(contact->depth < 0)
            {
                // should never happen, but just for safeness
                return 0;
            }
            contact->pos[0] = radius2 * vDir1[0] + SpherePos[0];
            contact->pos[1] = radius2 * vDir1[1] + SpherePos[1];
            contact->pos[2] = radius2 * vDir1[2] + SpherePos[2];
            contact->normal[0] = vDir1[0];
            contact->normal[1] = vDir1[1];
            contact->normal[2] = vDir1[2];
            contact->g1 = Cylinder;
            contact->g2 = Sphere;
            contact->side1 = -1;
            contact->side2 = -1;
            GeomCount++;
            return GeomCount;
        }
        else
        {
            // collision with the second disc
            contact->depth = (radius2 + length - s);
            if(contact->depth < 0)
            {
                // should never happen, but just for safeness
                return 0;
            }
            contact->pos[0] = radius2 * -vDir1[0] + SpherePos[0];
            contact->pos[1] = radius2 * -vDir1[1] + SpherePos[1];
            contact->pos[2] = radius2 * -vDir1[2] + SpherePos[2];
            contact->normal[0] = -vDir1[0];
            contact->normal[1] = -vDir1[1];
            contact->normal[2] = -vDir1[2];
            contact->g1 = Cylinder;
            contact->g2 = Sphere;
            contact->side1 = -1;
            contact->side2 = -1;
            GeomCount++;
            return GeomCount;
        }
    }
    return GeomCount;
}
